At present, when a FOUP which accommodates 300 mm wafers therein is placed on a dock plate (a docking table), V-shaped grooves provided on the bottom surface of the FOUP, having an angle of 90°, and assuming a shape resembling the inverted letter V are placed on three respective kinematic pins provided on the dock plate for positioning in the X-, Y-, and Z-directions (kinematic coupling).
Since FOUPs are resin moldings, angular deviation in the V-shape grooves varies. Some V-shape grooves have an angular deviation in excess of ±5°. Meanwhile, the kinematic pins are made of metal. A distal end portion of the kinematic pin; i.e., the distal end portion on which the corresponding V-shaped groove of the FOUP is placed, has its circumference formed into an R portion (a radiused portion) having a large curvature in order to lower contact pressure against two groove walls (two 45° slopes) of the V-shaped groove. Since the R portion of the kinematic pin has a complicated shape, direct measurement of its machining accuracy after machining is very difficult. Thus, under the present circumstances, kinematic pins manufactured by a plurality of manufacturers are used while their true machining accuracies are unknown or while their shape accuracies are inconsistent. Needless to say, variation of kinematic pins exists among different manufacturers. Even in the case of kinematic pins manufactured by the same manufacturer, variation exists among lots. However, there is no means of checking such variation.
Also, FOUPs are manufactured by a plurality of FOUP manufacturers, and load ports are manufactured by a plurality of load port manufacturers. Thus, there exists variation among FOUPs and among load ports stemming from difference in manufacturer. Also, there exists variation in accuracy caused by wear of the V-shaped grooves and the kinematic pins in the course of use over time. Thus, in the case where an arbitrary FOUP is placed on the dock plate of an arbitrary load port through kinematic coupling, theoretically, kinematic coupling is a positioning method which can ensure accuracy. However, in reality, this positioning method involves such a combination of components as to increase variation in accuracy and thus encounters difficulty in ensuring accuracy with respect to the height direction of the FOUP.
Meanwhile, at present, the standardization of various items associated with a 450 mm wafer is proceeding. The standardization of the slot pitch of a slot section of a FOUP for 450 mm wafers is proceeding on the basis of the same slot pitch of 10 mm as that of a FOUP for 300 mm wafers (even for a slot pitch in excess of 10 mm, standardization is proceeding so as to reduce slot pitch to as small a value as possible). When the 300 mm wafer and the 450 mm wafer have the same wafer thickness, in a state of being placed in a slot, a physical phenomenon of sag of the 450 mm wafer is about three times or more that of the 300 m wafer. Thus, as compared with the FOUP for 300 mm wafers, the FOUP for 450 mm wafers must be positioned with higher accuracy with respect to height; otherwise, a robot becomes highly likely to collide with a wafer accommodated in the FOUP (cracking of a wafer becomes highly likely to occur). Some 300 m and 450 mm wafers are very expensive products; specifically, the price of a product which has undergone the final process reaches tens of millions of yen. Thus, in handling wafers with the robot, the occurrence of such collision may incur a great loss.
The invention described in Patent Document 1 relates to a jig for measuring the position of a wafer in a FOUP, a jig for evaluating the shape of a kinematic pin, and a jig for evaluating the position of a kinematic pin.